A mechanical milking method of this type is nowadays used in many stables. In the case of this method a so-called teat cup is applied to the teats for milking. The teat cup consists of an outer stiff teat cup sleeve and an elastic tubular insert, the so-called teat rubber. The teat projects into the elastic hose member of the teat rubber during milking. Between the outer surface of the hose member of the teat rubber and the inner surface of the teat cup sleeve a so-called pulsator chamber is defined, which, during milking, has alternately applied thereto a vacuum in a so-called milking phase and atmospheric pressure in a so-called teat relief phase by means of a pulsator. The lower end of the teat is connected via a short hose to a so-called collecting piece, the short lines of the normally four teat cups, which are applied to the respective teats, ending in said collecting piece. The collecting piece communicates with a milk discharge line via a so-called long milk hose. A so-called milking vacuum is applied below the teat via the milk discharge line, the long milk hose and the respective short hoses. Discharge of the milk is achieved by continuously introducing a small stream of air under atmospheric pressure below the teat into the short hose or, in most cases, into the collecting piece.
The discharge of the milk depends to a decisive extent also on the interior cross-section of the hoses used, which have the milking vacuum applied thereto. Hoses having a small interior diameter of approx. 10 to 12 mm here offer the advantage of a particularly smooth discharge of the milk. Milk transport lines with a small interior diameter have, however, the disadvantage that the milking vacuum decreases strongly along the lines so that the vacuum which is actually applied below the teat becomes so low that the teat cups may perhaps fall off the teat, the milking time may become substantially longer, or sufficient emptying of the udder may no longer be guaranteed. In view of these and other reasons, hoses having a larger interior diameter and collecting pieces having larger volumes are increasingly used today so as to guarantee in this way that vacuum losses along the milk hoses are avoided as far as possible so that the nominal milking vacuum is actually applied below the teat without essential variations of the vacuum occurring below the teat.
Although varying milking vacuums, which have hitherto been used successfully, viz. e.g. vacuums between 35 kPa and 50 kPa, were not used in these systems having larger interior cross-sections of the milk transport hoses and a larger volume of the collecting piece, modifications of the teat ends occur when the new system is used. Contrary to all expectations, it has been found that the teat ends turn inside out and remain also in this condition when a prescribed milking unit is used for a prolonged period of time, i.e. it turned out that the teat ends were no longer capable of automatically closing completely, but remained open. Such a teat end is, however, exposed to extreme danger insofar as it may easily be attacked by bacteria whereby undesirable diseases of the udder will be caused. One of the consequences of the modification of the teat end and of the higher susceptibility to bateria resulting therefrom is that milk containing a higher percentage of somatic cells is delivered. Since the quality of the milk is, however, judged by the respective customers buying the milk according to the amount of cells contained in the milk, this will result in a reduction of the quality of the milk which will find expression in substantially lower milk prices.